JPH0712220B2 - Television receiver - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color television receiver, and more particularly to a circuit system suitable for adjusting contrast and brightness.

[Conventional technology]

Color cathode ray tubes used in color television receivers have variations in cut-off voltage and drive characteristics among the three primary colors R, G, B. Therefore, adjust the semi-fixed resistance for each television receiver. The variations were matched.

In recent years, research that automatically adjusts for this variation has become popular, and dedicated ICs are being commercialized. Eye
EEE, Transactions on Consumer Electronics, CE32, 3, August, 1986, pp251-257 (IEEE, Transactions on Co
nsumer Electronics, CE32, 3, August, 1986, pp251
The video output IC described in −257) has a function to automatically adjust the variation of the color cathode ray tube. The system of this IC will be described below.

Figure 2 shows the automatic adjustment function of the IC and the main parts around it. 10 is the IC, 21 is the luminance (Y) signal input terminal, 22 is the RY signal input terminal, and 23 is the BY. Input terminal, 24 is a contrast control circuit, 25 is a bright control circuit, 26 is a color saturation control circuit, 27 is a control circuit, 28 is an RGB matrix, 29, 30, 31 are cutoff drive detection signal insertion circuits, and 32 is Counter, 33, 37, 41 are variable amplifiers, 34, 38, 42 are DC shift circuits, 35, 36, 39, 40, 43, 44 are comparators, 1
11, 112, 113 are output amplifiers, 114, 115, 116 are output buffers, 48, 49, 50 are detection resistors, 51 is a color cathode ray tube, and 52 is a detection signal. Next, the operation will be described.

The brightness signal input to the brightness signal input terminal 21 is adjusted in gain by the contrast information sent from the control circuit 27 in the contrast control circuit 24, and the brightness control circuit
Similarly, at 25, the brightness is adjusted by the bright information and RGB
It is input to the matrix 28.

On the other hand, the color difference signals input to the RY signal input terminal 22 and the BY signal input terminal 23 are adjusted in color saturation by the color saturation control circuit 26 and then input to the RGB matrix 28.

The RGB matrix 28 produces and outputs RGB signals from the input luminance signal (Y) and color difference signals (RY, BY). The output R signal, for example, is sent to the cut-off drive detection signal insertion circuit 29, and the cut-off detection signal and the drive detection signal are sent from the counter 32 to a predetermined position (17H to 23H) of the video signal. Is inserted. The R signal in which the detection signal is inserted is controlled to a predetermined gain by the variable amplifier 33, and then controlled to a predetermined DC voltage by the DC shift circuit 34 and output from the IC 10. The output R signal is amplified to a predetermined level by the output amplifier 111, and the output buffer 114
Is input to the cathode of the color CRT 51.

As a result, the cathode current flows into the output buffer 114, and a voltage having a waveform similar to that of the input signal is generated in the detection resistor 48. The voltage generated by the detection resistor 48 is the beam current detection signal.
Returned to IC10 as 52. The returned detection signal 52 is
It is input to the comparators 35 and 36 and compared with the drive level reference voltage Vref1 and the cutoff level reference voltage Vref2. The comparison is made at the same time as when the detection signal is inserted by the cutoff drive detection signal insertion circuit 29 by the counter 32, and the inserted signal is the reference voltage Vref.
The gain of the variable amplifier 33 and the DC voltage of the DC shift circuit are adjusted so as to be equal to 1 and Vref2.

Similarly, the G signal system circuit and the B signal system circuit having the same circuit configuration as described above also perform the same operation, and finally the RGB cutoff and the drive level are adjusted so that a dark screen to a bright screen is displayed. The white balance of is automatically adjusted.

[Problems to be solved by the invention]

The above-mentioned prior art requires a circuit for adjusting the gain in two places inside the IC, that is, the contrast control circuit and the drive control circuit.
A circuit for adjusting the DC level was necessary at some places. In addition, it is necessary to adjust the gain or adjust the direct current of a video signal with a wide frequency band so as not to damage the frequency band, and to pass an excessive current to secure the frequency band,
Alternatively, it was realized by sacrificing the frequency band to some extent.

As a result, two circuits for adjusting the gain of the video signal and two circuits for adjusting the DC level of the video signal are required, which increases the number of elements, and an extra current must be supplied to secure the frequency band. was there.

An object of the present invention is to reduce the number of elements by reducing the number of elements by providing one circuit for adjusting the gain of the video signal and one circuit for adjusting the DC level of the video signal.

[Means for solving problems]

The purpose is to remove the contrast control circuit and instead provide a circuit for adjusting the voltage of the drive detection signal or the reference voltage of the drive level, or remove the bright control circuit and replace it with the voltage of the bright detection signal or This is achieved by providing a circuit that adjusts the cutoff level reference voltage.

[Action]

The drive detection signal voltage control circuit provided in place of the contrast control circuit changes the DC value of the drive detection signal according to the bright information and the contrast information sent from the control circuit. As a result, the relative relationship between the amplitudes of the drive detection signal and the video signal changes. Since the drive detection signal is fed back so that a constant beam current always flows, the luminance is always constant, but the relative relationship of the amplitude of the video signal with the drive detection signal changes, and as a result, the contrast changes. Thereby, the contrast can be controlled by changing the voltage of the drive detection signal in the drive detection signal voltage control circuit. At this time, the drive detection signal voltage control circuit does not require a frequency band as in the conventional contrast control circuit because the drive detection signal is a DC signal. Therefore, the circuit configuration becomes very simple. In addition, no extra bias current is required to secure the frequency band.

The cutoff detection signal voltage control circuit provided in place of the bright control circuit also performs the same operation as the above-mentioned contrast control circuit.

A drive level reference voltage control circuit provided in place of the contrast control circuit changes the reference voltage according to the bright information and the contrast information sent from the control circuit. As a result, feedback is applied so that the beam current that flows when the drive detection signal is output changes, so the contrast changes. Thereby, the contrast can be controlled by changing the drive level reference voltage by the drive level reference voltage control circuit. At that time, the drive level reference voltage control circuit
Since the reference voltage is a DC voltage, it does not require a frequency band unlike the conventional contrast control circuit. Therefore, the circuit configuration becomes very simple. No extra bias current is needed to secure the frequency band.

The cut-off level reference voltage control circuit provided in place of the bright control circuit also performs the same operation as the drive level reference voltage.

〔Example〕

The first embodiment of the present invention will be described below with reference to FIG.
In the figure, 101 is a cutoff level / drive level reference power supply, 102 is a counter, 103 is a power supply for a cutoff drive detection signal, 104 is a cutoff detection signal control circuit, and 105 is a drive detection signal control circuit. The same parts as those in FIG. 2 are designated by the same reference numerals.

Next, the circuit operation will be described. Since the same parts as those in FIG. 2 operate in the same manner, their explanations are omitted.

The cutoff level / drive level reference power supply 101 generates a cutoff level reference voltage and a drive level reference voltage, and sends them to the comparator. The counter 102 sets the cutoff detection period in the 1H period immediately after the VBLK period ends in the video sweep period, and sets the drive detection period in the next 1H period. Power supply for cut-off drive detection signal 103
Generates a DC voltage suitable for insertion. The generated DC voltage is sent to the cutoff detection signal control circuit 104 and the drive detection signal control circuit 105.

The cutoff detection signal control circuit 104 is the control circuit 2
The DC value of the cutoff detection signal is changed according to the bright information sent from 7. This cutoff detection signal is sent to the cutoff drive detection signal insertion circuits 29, 30, 31. Here, the cutoff drive detection signal insertion circuit 3
Since the operation of the circuits connected to 0 and 31 and thereafter is the same as the operation of the cutoff drive detection signal insertion circuit 29 and the circuits connected thereafter, the description thereof will be omitted.

The drive detection signal control circuit 105 includes a control circuit 27
The DC value of the drive detection signal is changed according to the bright information and the contrast information sent from the. This drive detection signal is sent to the cutoff drive detection signal insertion circuit 29.

The cutoff drive detection signal insertion circuit 29 inserts the video signal into the video signal at the insertion timing sent from the counter 102.
The cutoff detection signal and the drive detection signal are inserted as shown in FIG. The video signal into which each detection signal is inserted is input to the variable amplifier 33. The input video signal is the voltage at which the beam current value flowing as a result of being output to the cathode of the color cathode-ray tube 51 is detected by the detection resistor 48, and the cutoff level and drive level reference voltage output from the drive level reference power supply 101 and the comparator. The gain is controlled by the signal obtained by comparison at 35. At this time, the detection resistor 48
Since the gain control of the variable amplifier 33 is performed so that the voltage detected at 3 becomes equal to the drive level reference voltage, the drive detection signal always causes a constant beam current to flow.

Next, the gain-controlled video signal output from the variable amplifier 33 is input to the DC shift circuit 34. The input video signal includes the voltage detected by the detection resistor 48 and the cutoff level reference voltage output from the cutoff level / drive level reference power supply 101 and the comparator 36 as in the above.
The direct current level is controlled by the signal obtained by the comparison. At this time, since the DC control of the current shift circuit 34 is performed so that the voltage detected by the detection resistor 48 matches the cutoff level reference voltage, the cutoff detection signal always causes a constant beam current to flow.

By controlling the RGB3 system as described above, the beam current flowing through the color CRT 51 can be determined by the values of the detection resistors 48, 49, 50. Here, assuming that the beam current ratio of the color cathode-ray tube 51 is R: G: B = 1: 1: 1 and a predetermined white balance can be obtained, the values of the detection resistors 48, 49, and 50 should be the same. Thus, it is possible to obtain a predetermined white balance from dark white to bright white. Further, when it is desired to obtain an arbitrary white balance, it can be realized by changing the ratio of the detection resistors.

Now, with reference to FIG. 5, description will be made on the case where the information for increasing the contrast is inputted from the control circuit 27 to the drive detection signal control circuit 105.

In (a), when the contrast is typical, the peak of the image is almost the same as the peak of the drive detection signal, and the flowing beam current is also substantially the same.

When the information for maximizing the contrast is input from the control circuit 27 to the drive detection signal control circuit 105, the drive detection signal control circuit 105 lowers the level of the drive detection signal as shown in FIG. 5 (b). As a result, the beam current is feedback-controlled so as to be constant, so that the beam currents during the period of the drive detection signal are the same in FIGS. 5A and 5B, but the video signal is the same as the drive detection signal. Since it becomes relatively large, a large amount of beam current flows. Therefore, the contrast is controlled to max.

On the contrary, when the contrast is set to min, the operation is completely opposite to the above case, the beam current during the period of the drive detection signal is equal to that in the typical time, but the video signal is relative to the drive detection signal. The beam current is reduced because the beam current is reduced. Therefore, the contrast is controlled to min.

As described above, the drive detection signal is sent to the control circuit.
By controlling with the contrast information from 27, the contrast control can be performed.

Next, the case where the information for lowering the brightness from the control circuit 27 is input to the drive detection signal control circuit 105 and the cutoff detection signal control circuit 104 will be described with reference to FIG.

FIG. 6 (a) shows the case where the brightness is typical. The information that makes the brightness min from the control circuit 27 is the drive detection signal control circuit 105 and the cutoff detection signal control circuit 104.
When it is input to the drive detection signal control circuit 105 and the cutoff detection signal control circuit 104, the drive detection signal control circuit 105 and the cutoff detection signal control circuit 104 raise the levels of the drive detection signal and the cutoff detection signal, as shown in FIG. 6B. As a result, the beam current is feedback-controlled so as to be constant, so that the beam currents in the periods of the cutoff detection signal and the drive detection signal are the same in FIGS. 6A and 6B, but the video signal is Since the direct current is shifted to be relatively low with respect to the cutoff detection signal and the drive detection signal, the entire video signal becomes dark and the dark portion sinks in black.
Therefore, bright is controlled to min.

On the contrary, when the brightness is set to max, the operation opposite to the above case is performed and the beam current during the period of the cutoff detection signal and the drive detection signal is equal to the typical time, but the video signal is cut. Since the direct current is shifted higher relative to the off detection signal and the drive detection signal,
The entire video signal becomes bright. Therefore, bright is controlled to max.

Bright control can be performed by controlling the cutoff detection signal and the drive detection signal by the bright information from the control circuit 27 as described above.

The cutoff detection signal control circuit 104 and the drive detection signal control circuit 105 used for the contrast control and the bright control may be an amplifier capable of varying the DC level, so as to vary the gain of a video signal having a wide frequency band. Since a simple amplifier is not required, the circuit configuration becomes simple. As one embodiment of this, FIG. 7A shows a conventional contrast control circuit 24 and a bright control circuit 25, a cutoff detection signal control circuit 104 of the present invention is shown in FIG. 7B, and a drive detection signal control circuit 105. Is shown in (c). Further, the bias current required to secure the frequency band does not need to have a wide frequency band, so that the current value can be reduced.

Further, the drive cutoff detection signal power supply 103 may be replaced with a power supply that is directly controlled by the contrast information and the bright information from the control circuit 27. The cutoff detection signal control circuit 104 and the drive detection signal control circuit 1
05 and drive cutoff detection signal power supply 103 are the 7th
It can be realized by a circuit configuration in which a DC voltage is supplied to the DC input shown in FIGS.

Next, a second embodiment of the present invention will be described with reference to FIG. In the figure, 107 is a cut-off level reference voltage control circuit, 106 is a drive level reference voltage control circuit, and the same parts as those in FIGS. 1 and 2 are designated by the same reference numerals.

Next, the circuit operation will be described. Since the same parts as those in FIGS. 1 and 2 operate in the same manner, the description thereof will be omitted.

The drive level reference voltage control circuit 106 inserted between the cutoff level / drive level reference power supply 101 and the comparator 35 changes the reference voltage of the comparator according to the contrast information sent from the control circuit 27. As a result, the drive level beam current value changes. In addition, the cutoff level reference voltage control circuit 107 inserted between the cutoff level / drive level reference power supply 101 and the comparator 36 is the DC of the reference voltage based on the bright information and the contrast information sent from the control circuit 27 in the same manner. The value changes. As a result, the beam current values at the cutoff level and the drive level change.

Now, from the control circuit 27, set the contrast to ma
When the information to be increased to x is input to the drive level reference voltage control circuit 106, the drive level reference voltage becomes high. Therefore, control is performed to match the level of the drive detection signal with the increased reference voltage, so that the beam current in the period of the drive detection signal increases as shown in FIG. 8 (b). As a result, the beam current at the peak of the video signal also increases, resulting in higher contrast.

On the contrary, when the information for lowering the contrast is sent from the control circuit 27, the operation reverse to the above is performed, the beam current at the peak is reduced, and the contrast is lowered.

As described above, the drive level reference voltage can be controlled by the contrast information from the control circuit 27.

Next, when information for increasing the brightness to the maximum is input from the control circuit 27 to the drive level reference voltage control circuit 106 and the cutoff level reference voltage control circuit 107, the drive level reference voltage and the cutoff level reference voltage increase. Therefore, control is performed so as to match the level of the period of the cutoff detection signal and the level of the period of the drive detection signal with the increased reference voltage, so that the period of the cutoff detection signal as shown in FIG. And the beam current during the period of the drive detection signal increases. As a result, the average beam current of the video signal increases, resulting in a brighter image.

On the contrary, when the information for lowering the brightness is sent from the control circuit 27, the operation reverse to the above is performed, the average beam current of the video signal is decreased, and the brightness is decreased.

As described above, by controlling the cutoff level reference voltage and the drive level reference voltage with the bright information from the control circuit 27, bright control can be performed.

The drive level reference voltage control circuit 106 may be a circuit as shown in FIG. 7 (c), and the cutoff level reference voltage control circuit 107 may be a circuit as shown in FIG. 7 (b). As a result, the conventional circuit for controlling contrast and brightness as shown in FIG. 7A can be eliminated, and the circuit configuration becomes simple. Further, the bias current required to secure the frequency band does not need to have a wide frequency band, so that the current value can be reduced.

Furthermore, cut-off level and drive level reference power supply 10
It suffices to replace 1 with a power supply that is directly controlled by contrast information and bright information from the control circuit 27, and a cutoff level reference voltage control circuit 107, a drive level reference voltage control circuit, and a cutoff level / drive level reference power supply. 101 can be realized by a circuit configuration in which a DC voltage is supplied to the DC input shown in FIGS. 7B and 7C by resistance division or the like.

Even if the circuit configuration for detecting and returning the beam current as shown in the first and second embodiments is not used, a circuit as shown in FIG. 9 is attached to the output of the IC for feedback. In this way, this circuit can be used for contrast control and bright control of a model in which the cutoff and drive are adjusted by the semi-fixed resistance of the one-stage television receiver.

〔The invention's effect〕

According to the present invention, the number of elements can be reduced by inserting a simple circuit capable of varying the DC voltage instead of the conventional contrast control circuit and bright control circuit. In addition, the bias current required to secure the frequency band can be reduced, which has the effect of reducing the power consumption of the IC.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention, FIG. 2 is a circuit diagram showing a conventional method for controlling contrast and brightness, and FIG. 3 is a circuit showing a second embodiment of the present invention. 4 and 5 are waveform diagrams showing a video signal in which a cutoff detection signal and a drive detection signal are inserted, and FIG. 5 is a waveform diagram illustrating contrast control according to the first embodiment of the present invention. Is a waveform diagram for explaining the bright control according to the first embodiment of the present invention, FIGS. 7 (a), (b), and (c) are circuit diagrams showing a contrast and bright control circuit, and FIG. FIG. 9 is a waveform diagram for explaining contrast and brightness control according to the second embodiment of the present invention, and FIG. 9 is a circuit diagram showing an external circuit when the present invention is used in a conventional television receiver. 101 …… Cut-off level / drive level reference power supply, 1
02 …… Counter, 103 …… Cutoff drive detection signal power supply, 104 …… Cutoff detection signal control circuit, 105…
... Drive detection signal control circuit, 106 ... Drive level reference voltage control circuit, 107 ... Cutoff level reference voltage control circuit, 29,30,31 ... Cutoff drive detection signal insertion circuit, 33,37,41 ... … Variable amplifier, 34,38,42 …… DC shift circuit, 35,36,39,40,43,44 …… Comparator, 48,49,50
...... Detection resistance.

Front Page Continuation (72) Inventor Toshinori Murata, 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Prefecture Home Appliances Research Laboratory, Hitachi, Ltd. (56) References JP 62-268292 (JP, A) JP 60- 186187 (JP, A)

Claims (6)

[Claims] 1. An insertion circuit for inserting a predetermined signal into a video signal, a gain variable circuit for controlling the gain of the video signal obtained by the insertion circuit, and a DC voltage of the video signal obtained by the gain variable circuit. A direct current control circuit for controlling the above, a detection circuit for detecting a beam current flowing as a result of outputting the video signal obtained by the direct current control circuit, and a first and a comparison circuit for comparing the detection signal obtained by the detection circuit with a reference signal. A second comparison circuit, a timing circuit that determines the operation timing of the insertion circuit and the first and second comparison circuits, and a signal output from the first comparison circuit to control the gain of the gain variable circuit. A television receiver comprising: first control means; and second control means for controlling the direct current of the direct current control circuit with a signal output from the second comparison circuit, An insertion signal control circuit for controlling the insertion signal inserted by the insertion circuit, and a third control means for controlling the insertion signal controlled by the insertion signal control circuit with a signal for controlling contrast and / or bright. A television receiver characterized by having. 2. An insertion circuit for inserting a predetermined signal into a video signal, a gain variable circuit for controlling the gain of the video signal obtained by the insertion circuit, and a DC voltage of the video signal obtained by the gain variable circuit. A direct current control circuit for controlling the above, a detection circuit for detecting a beam current flowing as a result of outputting the video signal obtained by the direct current control circuit, and a first and a comparison circuit for comparing the detection signal obtained by the detection circuit with a reference signal. A second comparison circuit, a timing circuit that determines the operation timing of the insertion circuit and the first and second comparison circuits, and a signal output from the first comparison circuit to control the gain of the gain variable circuit. A television receiver comprising: first control means; and second control means for controlling the direct current of the direct current control circuit with a signal output from the second comparison circuit, A reference signal control circuit for controlling a reference signal compared by the first and second comparison circuits, and a fourth control circuit for controlling the reference signal controlled by the reference signal control circuit with a signal for controlling contrast and / or brightness. And a control means for the television receiver. 3. A television receiver according to claim 1, wherein the third control means is a contrast control means. 4. A television receiver according to claim 2, wherein the fourth control means is a contrast control means. 5. The television receiver according to claim 1, wherein the third control means is a bright control means. 6. A television receiver according to claim 2, wherein the fourth control means is a bright control means.